This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Oncostatin M (OSM) is a pleiotropic cytokine produced by many cell types, including neutrophils and tumor-associated macrophages. OSM inhibits the proliferation of breast cancer cells in vitro, and for this reason is being examined for its potential use in cancer treatment. Important to this endeavor are the results of preliminary studies done in our laboratory that show that OSM may promote pro-angiogenic factors in tumor cells, as is observed for endothelial cells. Additional studies show that OSM is expressed by tumor-associated neutrophils and breast cancer epithelial cells, but not by normal breast tissue. Furthermore, neutrophils isolated from whole blood do not express OSM until they are co-cultured with breast cancer cells. Our data demonstrates that OSM will stimulate breast cancer cells to produce angiogenesis-related matrix metalloproteinases (MMPs) and vascular endothelial growth factor-A (VEGF), which is an extremely potent pro-angiogenic factor. The implication of the latter finding is that while OSM may cause growth-arrest in breast cancer cells in vitro, it may also lead to the induction of angiogenesis in the tumor through production of VEGF. Such an induction of angiogenesis would counter the growth arrest properties of OSM by promoting angiogenesis-dependent breast cancer progression. In light of our findings, it is important to better understand the implications of VEGF induction to correctly evaluate the potential of OSM as a clinical cancer treatment. The Specific Aims of the proposal are: SPECIFIC AIM 1. DEMONSTRATE THAT NEUTROPHIL-DERIVED OSM WILL INDUCE VEGF FROM BREAST CANCER CELLS IN A PARACRINE FASHION. Neutrophils will secret OSM when they are co-cultured with breast cancer cells, but the pathophysiologic significance of this is unknown. Neutrophil-breast cancer cell co-cultures will be tested to determine whether neutrophil-secreted OSM will induce VEGF from breast cancer cells in a paracrine fashion. OSM and VEGF levels will be analyzed by ELISA. SPECIFIC AIM 2. IDENTIFY AND CHARACTERIZE THE SIGNAL THAT STIMULATES NEUTROPHILS TO RELEASE OSM. We will identify the signal generated by breast cancer cells that stimulates neutrophils to release OSM by performing Western blots/ELISAs on cell lysates/conditioned media of co-cultured cells treated with neutralizing antibodies to specific cytokines such as GM-CSF. In addition, we will determine whether neutrophil-breast cancer cell contact is needed for release of OSM by neutrophils in both a co-culture system (cell-contact) and a Transwell-culture (no cell contact). SPECIFIC AIM 3. INVESTIGATE THE ABILITY OF OSM-INDUCED VEGF TO STIMULATE ANGIOGENESIS AND PROMOTE BREAST CARCINOMA PROGRESSION IN VIVO. We will investigate whether OSM-induced VEGF will stimulate angiogenesis in vivo using the Matrigel plug assay, and assess whether OSM-transfected breast cancer cells injected into the cleared mammary fat pads of nude mice will promote tumor progression by stimulating VEGF-dependent angiogenesis in an autocrine fashion.